GB2072270A

GB2072270A - Hand-starting mechanism for an internal combustion engine

Info

Publication number: GB2072270A
Application number: GB8100793A
Authority: GB
Original assignee: Farymann Diesel GmbH
Current assignee: Farymann Diesel GmbH
Priority date: 1980-03-20
Filing date: 1981-01-12
Publication date: 1981-09-30
Also published as: ES8204500A1; ES500442A0; IT1170696B; DE3010727A1; IT8147746A0; JPS56165765A; GB2072270B; US4353335A

Description

1

SPECIFICATION A hand-starting mechanism for an internal combustion engine

This invention relates to a hand-starting mechanism for an internal combustion engine 70 which comprises an axially displaceable starting shaft, a starting handle attached to an outer end of the starting shaft, and a one-way dog coupling provided at an inner end of the starting shaft for coupling the starting shaft to a shaft to be cranked 75 of an internal combustion engine during a starting procedure and for uncoupling the shaft, by axially separating the shafts, when the engine starts running.

Safety regulations for hand-starting mechanisms require today a safety device against kickback of the starting handle. Kockback occurs when the internal combustion engine does not overcome the upper dead centre when firing, thus generating a movement opposite to its normal sense of rotation. Due to this wrong movement the engine operator receives a blow on his hand and arm which may cause injuries and is always painful. In order to prevent this danger, antikickback devices are used consisting of a freewheel device which prevents the kickback movement and permits the starting movement. Normally and also for example in the starting mechanism according to British patent No.

1 562 677, the starting shaft is rigidly connected with an inner rotary part of the freewheel device. This has the disadvantage that the freewheel device has to support the full force of the kickback. In the starting mechanism according to British patent No. 1 562 677, the starting handle is connected to the starting shaft via a yieldable entrainment device in order to avoid the abrupt stopping of the cranking movement by the blocked freewheel device.

An object of the invention is to avoid the aforementioned disadvantage and also the expense for the yieldable entrainment device.

According to the invention there is provided a hand-starting mechanism for an internal combustion engine comprising:

an axially displaceable starting shaft; a starting handle attached to an outer end of the starting shaft; a one-way dog coupling provided at an inner end of the starting shaft for coupling the starting 115 shaft to a shaft to be cranked of an internal combustion engine during a starting procedure and for uncoupling the shaft, by axially separating the shafts, when the engine starts running; 55 a freewheel device through which the starting 120 shaft extends, the device having a stationary outer part and an inner part which is rotatable in one direction relative to the outer part; and coupling elements provided on the starting shaft and on said inner part of the free wheel device which are interengageable in such a way that (1) during a starting rotation of the starting shaft, said inner part is rotated in said one direction and, (2) in the event of a kickback from GB 2 072 270 A 1 the shaft of the engine (when said inner part of the free wheel device will be held stationary), said coupling elements react so as to effect axial displacement of the starting shaft in a direction away from the engine shaft whereby the one way dog coupling becomes disengaged.

Preferably, said coupling elements comprise a drive pin provided on the starting shaft and clawlike recesses provided on said inner part of the free wheel device, said recesses having entrance ramps which are engageable slideably with said driving pin during an engine kickback in order to effect said axial displacement of the starting shaft.

Therefore, it becomes possible for throw-off claws of a one way dog coupling to become separated from a drive pin of the engine shaft after a very small travel of the starting shaft in the kickback direction, during which the freewheel device has only to support the very small frictional force which occurs when the drive pin slides over the entrance ramps of the recesses of the inner rotary part of the freewheel device. This very small kickback movement of the starting shaft cannot be felt at the handle and the cranking movement will not be stopped abruptly due to the nearly instantaneous separation of the starting shaft from the shaft to be cranked.

Advantageously a pushing-out of the starting shaft together with the starting handle when the internal combustion engine fires or kicks back is avoided by providing the starting shaft on its outer circumference with axially inner and outer circumferential grooves into each of which can snap an axially immovable spring loaded locking pin, the locking pin being located in the outer groove when the one way dog coupling is engaged and being located in the inner groove when the one way dog coupling is disengaged.

The introduction of the starting shaft and handle during the starting procedure is facilitated advantageously by providing the starting shaft with threaded portions between the outer circumferential groove and the inner frontal face of the starting shaft into which the spring loaded locking pin is engageable so that the starting shaft is screwed axially in inward direction on the threaded portions when turned in the starting sense until the one way dog coupling becomes engaged.

Advantageously the separation of the claws of the one way coupling from the drive pin of the shaft to be cranked is facilitated by the claws being provided with drive faces extending parallel to the axis of the starting shaft in the vicinity of its inner frontal face.

The same advantageous purpose is served by a design according to which the drive pin of the shaft to be cranked is rounded off at its side facing the starting shaft.

One embodiment of hand-starting mechanism according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a longitudinal section of the mechanism with an engaged dog coupling; 2 Figure 2 is a longitudinal section of the mechanism with disengaged dog coupling; Figure 3 is a view of throw-off claws at the inner frontal face of the starting shaft, seen in the direction of the arrow 111; Figure 4 is a cut out of a frontal view of the freewheel device seen in the direction of the arrow IV; Figure 5 is a longitudinal section along the line V-V in Figure 6 of an inner rotary part of the 75 freewheel device; Figure 6 is a front view of the inner rotary part shown in Figure 5 seen in the direction of the arrow VI; and Figure 7 is a development of the profile of the frontal recesses and ramps of the inner rotary part.

Figures 1, 2, 3 and 4 are drawn in a scale 2:1.

Figures 5, 6 and 7 are drawn in a scale 1:1.

As shown in Figures 1 and 2 a starting handle 1 is fastened rigidly with the aid of welding seam 2 to the outer frontal face 3 of a starting shaft 4. At the inner frontal face 5 of the starting shaft 4 are formed two starting claws 6 with their inclined throw-off faces 7 (Figure 3) and their entrainment faces 8. The latter are arranged parallel to the axis of the starting shaft 4. The faces 7 and 8 of the starting claws 6 form a one way dog coupling together with an entrainment pin 9. The entrainment pin 9 is fastened rigidly to a shaft 10 to be cranked (belonging to an internal combustion engine of which only the housing portion 11 is visible). The shaft 10 is, in the example shown in Figures 1 and 2, the cam shaft of a four-stroke internal combustion engine. The shaft 10 is supported by a ball bearing 12 and sealed by a lip seal 13. The entrainment pin 9 is rounded off at its side 14 (Figure 2) facing the starting shaft 4. In the position shown in Figure 1, a locking pin 16 which is loaded by a spring 15 has snapped into an outer circumferential groove 17 of the starting shaft 4, the one way dog coupling (6, 7, 8, 9) being engaged. In the position of the starting shaft 4 shown in Figure 2 (displaced axially outwardly relative to shaft 10) the locking pin 16 has snapped into a further, inner circumferential groove 18 provided in the starting shaft 4. The starting shaft 4 also is provided with threaded portions 19 which form part of a double helical thread. The starting shaft 4 has an outer entrainment pin 20 which engages during the starting procedure, i.e. in the position shown in Figure 1, two claw-like frontal recesses 21 an the inner rotary part 22 of a free-wheel device consisting of the part 22, clamping elements 23 (Figure 4), and an outer ring 24. The 120 latter is connected rigidly with the housing 11.

The recesses 21 continue into frontal ramps 25 and 26 (Figures 5, 6, 7) of the inner rotary part 22.

The freewheel device 22, 23, 24 is closed at its outer side by a cover plate 27 rolled over the outer 125 ring 24. Rubber rings 28 and 29 are provided to seal the faces which are in relative movement.

The operation of the above described hand starting mechanism is as follows:

For starting, the starting shaft 4 is put axially 130 GB 2 072 270 A 2 into the mechanism with the aid of the starting handle 1 until the locking pin 15 snaps into the circumferential groove 18, when the shaft 4 is in the position shown in Figure 2. Now the starting handle 1 is turned in the starting sense (in the view of Figures 4 and 6 counterclockwise). Since, the rubber rings 28 and 29 have a certain frictional effect the inner rotary part 22 remains stationary so that the starting shaft 4 is screwed in inward direction on the threaded portions 19 which are in contact with the locking pin 16. During this movement the entrainment pin 20 slides either along the ramps 25, 26 or will be drawn directly into the recesses 21 if its position permits it. (The pin 20 and recesses 21 with ramps 25 and 26 form interengageable coupling elements provided on the starting shaft and on the inner part of the free wheel device which operate in such a way that, during a starting rotation of the starting shaft, the inner part is rotated in one direction relative to the outer part, but in the event of a kickback from the engine shaft, the inner part is held stationary and the coupling elements react so as to effect axial displacement of the starting shaft in a direction away from the engine shaft whereby the one way dog coupling becomes disengaged.) Thereupon the inner part 22 rotates in relation to the outer ring 24, which movement is permitted by the clamping element 23. During this movement the entrainment pin 9 slides along the throw-off faces 7 until it stops at the entrainment faces 8 (Figure 1). As a consequence the shaft 10 is entrained with the movement of the starting shaft 4 and the internal combustion engine is cranked. If the engine starts running regularly, the entrainment pin 9 moves away clockwise (with respect to Figure 3) from the entrainment faces 8 and slides over the throw-off faces 7, pushing the shaft 4 axially outwards, which causes the locking pin 16 to jump out of the groove 17 and to snap into the groove 18. If the internal combustion engine does not fire regularly but kicks back, the entrainment faces 8 remain in contact with the entrainment pin 9 which turns the starting shaft counterclockwise (with respect to Figure 3) by a small amount. This corresponds to a small movement of the entrainment pin 20 in clockwise direction (with respect to Figures 4 and 6) which causes the pin 20 to slide axially outwards on the ramps 25 and move the shaft 4 until the edges of the entrainment faces 8 are in the position on the surface 14 shown in broken lines in Figure 2. Thereupon the edges slide over the surface 14 of the entrainment pin 9 which causes the starting shaft 4 to move into the position shown in full lines in Figure 2. During this movement the clamping elements 23 prevent any clockwise (with respect to Figure 4) movement of the part 22 relative to the outer ring 24 so that the entrainment pin 20 can slide in outward direction on the ramps 25. Due to the smallness of this movement the engine operator is protected effectively against a blow on his hand and arm. The ensuing quick disengagement of the one way dog coupling causes an instantaneous free 3 GB 2 072 270 A 3 turnability of the starting handle in the starting sense.

Claims

1. A hand-starting mechanism for an internal combustion engine comprising:

an axially displaceable starting shaft; a starting handle attached to an outer end of 45 the starting shaft; a one-way dog coupling provided at an inner end of the starting shaft for coupling the starting shaft to a shaft to be cranked of an internal combustion engine during a starting procedure and for uncoupling the shaft, by axially separating the shafts, when the engine starts running; a free wheel device through which the starting shaft extends, the device having a stationary outer part and an inner part which is rotatable in one direction relative to the outer part; and coupling elements provided on the starting shaft and on said inner part of the free wheel device which are interengageable in such a way that (1) during a starting rotation of the starting 60 shaft, said inner part is rotated in said one direction and, (2) in the event of a kickback from the shaft of the engine (when said inner part of the free wheel device will be held stationary), said coupling elements react so as to effect axial 65 displacement of the starting shaft in a direction away from the engine shaft whereby the one way dog coupling becomes disengaged.

2. A hand-starting mechanism according to claim 1, in which said coupling elements comprise 70 a drive pin provided on the starting shaft and claw-like recesses provided on said inner part of the freewheel device, said recesses having entrance ramps which are engageable slideably with said driving pin during an engine kickback in order to effect said axial displacement of the starting shaft.

3. A hand-starting mechanism according to claim 1 or 2, including an axially inner and outer circumferential groove provided on the circumference of the starting shaft, and a spring loaded axially immovable locking pin which can snap into either of said circumferential grooves, the locking pin being located in the axially outer circumferential groove when the one way dog coupling is engaged and being located in the axially inner circumferential groove when the one way dog coupling is disengaged.

4. A hand-starting mechanism according to claim 3, in which the starting shaft is provided with threaded portions between said inner and outer circumferential grooves, said spring loaded locking pin being arranged to snap into the threaded portions so that the starting shaft is screwed on the threaded portions axially in inward direction when the shaft is rotated in the starting direction until the one way dog coupling becomes engaged.

5. A hand-starting mechanism according to any one of the preceding claims, in which the one way dog coupling has throw-off claws provided with driving faces extending parallel to the axis of the starting shaft in the vicinity of its inner end.

6. A hand-starting mechanism according to claim 5, in combination with an engine shaft, in which a drive pin connected to said engine shaft for cooperating with said throw-off claws is rounded at its side facing the starting shaft.

7. A hand-starting mechanism according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.